Traditionally industrial gases used in larger quantities as a utility have been compressed and sent down pipelines under high pressure to transport the gas to one or more industrial gas customers. The high pressure in the pipeline is used for transport and gas storage. When the gas has arrived at it's use point, the pressure of the industrial gas is reduced by passing it through one or more control valves and/or pressure regulators to it's final pressure for consumption. Typically, one or more of the industrial gas customers will need the gas at a much lower pressure than is required by the transportation pipeline. The available energy and the chilling effect from the reduction in the pressure of the industrial gas to be consumed is wasted in the control valves and pressure regulators for the gas sent to the customers. Furthermore, due to the nature of the pipeline controls, some of the industrial gas manufactured and compressed into the pipeline must be vented to the atmosphere through control valves and pressure regulators when the customer demand does not closely match the design capacity of the pipeline compressors. Centrifugal pipeline compressors, due to seasonal cooler ambient temperatures also experience large increases in capacity. The available energy and chilling capacity in this gas is also wasted.
While industrial gas companies have compressed industrial gas into merchant liquid units for many years, none have attempted to recover the potential merchant capacity inherent in the high pressure transportation pipelines supplying lower pressure industrial gas customers. The letdown liquefaction units described herein will opportunistically take advantage of the ability of the pressure reduction already occurring to make merchant liquid products, which include liquid nitrogen, liquid oxygen, liquid air, liquid carbon monoxide and liquid argon.